The simplest type of suspension for drive units in this case is the nose-suspension drive. DE 195 30 155 A1 describes a solution of this type in which the motor is supported on one side by two nose bearings on the wheel axle of the driving wheels and is held on the bogie on the other side in a sprung manner. In this arrangement motor and transmission are disposed so as to ride on the axle. With this type of drive the mass of the motor and transmission rests for the most part unsprung on the wheelset. The disadvantage of this nose-bearing connection is that forces (accelerations) resulting from track unevennesses are transferred directly to the drive. This effect is amplified as the speed increases. Large unsprung masses or moments of inertia of the primarily sprung masses give rise to instabilities and very high forces between wheel and rails, thus making other solutions necessary.
The horizontal oscillation characteristics in particular become detrimentally noticeable at speeds in excess of approximately 140 km/h, wherein a translational oscillation having an amplitude that is directed transversely relative to the track is generally overlaid with a rotary oscillation about a perpendicular axis to produce a rocking motion.
This problem of running stability or running safety with regard to driven rail vehicles is addressed in various ways.
For example, use is frequently made of the effect that is generally known in technological terms as absorption, in order to influence lateral oscillations and rotary oscillations about the normal axis of the chassis and thereby significantly to improve the stability of the vehicle. In the case of absorption characteristic frequencies of the bogie or locomotive are overlaid and attenuated by the oscillation of an additional oscillating mass.
This effect is achieved by decoupling the masses of the drive from the rest of the chassis. In terms of operational running (unstable running characteristics), decoupling is primarily necessary at high speeds, which is why heavy locomotive drives having axle-mounted transmission operate at speeds of up to only 160 km/h at present.
In locomotive bogies for high speeds of up to and exceeding 300 km/h, use is made of e.g. fully sprung hollow shaft drives. In this case motor and transmission are decoupled from the wheelset and the transfer of force to the wheelset takes place via a hollow shaft which encloses the whole wheelset shaft. This solution is very expensive and heavy due to its complex, resource-intensive construction.
EP 0 444 016 B1 shows an example of such a solution. In this case the running motor and the flanged transmission are elastically suspended in the bogie frame via vertically disposed leaf springs in each case, and therefore act jointly as absorbers for lateral and rotary oscillations about the normal axis of the bogie. This solution has disadvantages in terms of the complex and resource-intensive construction, the considerable weight and the high costs caused by the requirement for the installation of a hollow shaft.
A bogie is known from EP 0 589 866 B1. In that case, however, the transmission is directly flanged onto the running motor and the motor transmission unit is suspended in the bogie by means of sprung elements. In addition to the considerable weight, the complex, resource-intensive construction and the high costs of this solution are disadvantageous.